Automated stacking devices, sometimes referred to as “palletizers,” are often used in factory settings to organize or stack items. The items these palletizers stack may include a variety of things, such as boxes made from corrugated board, paperboard, and/or fiberboard. The items are usually stacked onto frames or pallets made of wood, metal, and/or plastic. These pallets hold the products for transportation purposes.
One problem with conventional palletizers comes when items are stacked successively on top of each other. Many conventional palletizers, when attempting to stack a second item on top of a previously stacked item, alter the position of the previously stacked item. For example, a conventional palletizer may accidentally knock over a previously stacked box when attempting to place a second box on top of the previously stacked box.
Also, many conventional palletizers convey items to be stacked along conveyor belts. These conveyor belts may make contact with a previously stacked item as they convey a second item and cause the previously stacked item to be displaced when making contact with the conveyor belt. In an attempt to solve the problem of the conveyor belts coming into contact with previously stacked items, some conventional palletizers attempt to vertically separate the conveyor belt assembly sufficiently far away from the stack in hopes that the conveyor belt and/or palletizer does not come into contact with previously stacked items. Unfortunately, with this solution, the conveyor belt assembly carrying the second item is now too far away from the previously stacked item, thereby causing the second item to be dropped from excessive heights onto the previously stacked, which can result in the stacked items becoming damaged upon impact.
Other conventional stacking apparatuses utilize progressively thinner metal forks to stack items. One such apparatus is disclosed in U.S. Pat. No. 4,902,195, titled “Device for Automatically Piling up Flat Elements,” issued Feb. 20, 1990 (“the '195 patent), and incorporated by reference herein in its entirety. Stacking apparatuses of this type often employ a backstop mechanism, such as item 33 of the '195 patent, where the metal forks are retracted against such backstop mechanisms to place an item on top of a previously stacked item. In these apparatuses, the metal forks can be placed close to the previously stacked item. Unfortunately, the drag of the metal fork pulling back on the item against the backstop can alter the position of a previously placed item and/or leave marks on the item being stacked.
As part of the automated stacking process, stacking devices often perform two basic operations—lifting and squaring. Lifting generally involves moving items to appropriate vertical positions for stacking whereas squaring generally involves aligning multiple items to each other such that the items form right angles. Conventional stacking devices often employ squaring mechanisms along with the lifting mechanisms. This may result in slower overall throughput of the stacking device, for example, in some conventional approaches, the lift mechanism must remain in place until a stack of items is completed and exited the squaring mechanism. The apparatus disclosed in the '195 patent has this problem as it includes a vertically movable table 7 with the backstop mechanism 33 attached. Items 71 enter the stacking device on the vertically movable table 7 and the backstop 33 is used to square items after they are placed on the stack. See e.g., FIG. 3 of the '195 patent. Because the backstop 33 is actually part of the table 7, the table 7 remains stationary until the item 71 has been squared by the backstop 33 and may be limited from obtaining another item to place on the stack. As a result, the overall throughput of the stacking device is limited.
Accordingly, there is a continuing need in the art for automated stacking devices that overcome one or more of the limitations of conventional approaches.